An active matrix display device, in which thin film transistors (hereinafter, “TFTs”) or like devices are used as switching elements for pixels, is quick to respond and easy to achieve a grayscale display. Due to these advantages, the active matrix display device has been used recently in a broad range of applications, such as mobile phones, mobile game machines, onboard navigation devices, as well as in television sets.
The active matrix display device generally includes an active matrix substrate and a counter substrate which are disposed so as to face each other, with a display element (liquid crystal, organic EL, etc.) being disposed between the substrates and sealed with a sealant.
Meanwhile, display devices, in which a scan signal line drive circuit, a data signal line drive circuit, etc. are formed monolithically on an active matrix substrate, allow for compact frame areas and improved reliability, and therefore preferentially being used in mobile information terminals, such as mobile phones and mobile type game machines.
(Active Matrix Substrate)
Referring to FIG. 9, the following will describe a schematic arrangement of an active matrix substrate in which a scan signal line drive circuit is formed monolithically. FIG. 9 is a plan view illustrating a schematic arrangement of a major part of the active matrix substrate.
As illustrated in FIG. 9, the active matrix substrate 20 has a display area 22 which is formed at a central part of an insulating substrate 21 made from, for example, a glass substrate. In the display area 22 are there formed pixel electrodes (not shown), display driver TFT elements (switching elements; not shown), etc. in a matrix manner. Each display driver TFT element has a gate electrode connected to a scan signal line 30, a source electrode connected to a data signal line 31, and a drain electrode connected to a pixel electrode (not shown). The scan signal lines 30 and the data signal lines 31 are disposed so as to intersect at right angles with each other in the display area 22 of the active matrix substrate 20. Note that the scan signal lines 30 and the data signal lines 31 are disposed in different layers on the active matrix substrate 20 with an intervening insulating layer therebetween, so that they are not electrically connected to each other at the intersections.
A frame area 24 is formed in an area surrounding the display area 22 near a substrate perimeter 26 of the active matrix substrate 20. Scan signal line drive circuits 32 are provided in the right and left (with respect to a direction indicated by arrow X in FIG. 9) portions of the frame area 24 so as to sandwich the display area 22. The scan signal line drive circuits 32 are electrically connected to the scan signal lines 30 to apply scan signals to the scan signal lines 30.
Since the scan signal line drive circuits 32 are provided in both the right and left portions of the frame area 24 so as to sandwich the display area 22, when a signal is fed to a scan signal line 30 from both the right and left sides, signal waveform distortion is reduced. Thus, the driver TFT elements which constitute the scan signal line drive circuits 32 can be reduced in size, and it is possible to provide an active matrix substrate 20 with a narrower frame area 24. In contrast, even when a signal is fed to a scan signal line 30 from either the right or left side, the frame area 24 can be sized equally on the right and left sides of the active matrix substrate 20 by dividing the scan signal lines 30 into a group which is driven by the right-side scan signal line drive circuit 32 and a group which is driven by the left-side scan signal line drive circuit 32.
A driver 33 is provided in either the top or bottom (with respect to a direction indicated by arrow Y in FIG. 9) portion of the frame area 24. The driver 33 is electrically connected to the data signal lines 31 to apply data signals to the data signal lines 31.
Wiring 35, including clock wires, which is provided for the scan signal line drive circuits is connected to terminals 34 formed by, for example, a patterned thin metal film, so as to supply signals needed to operate the scan signal line drive circuits 32 from an external DC/DC converter, an external display control circuit, etc. via FPCs (flexible printed circuits; not shown), etc.
Note that the active matrix substrate 20 shown in FIG. 9 includes two scan signal line drive circuits 32, one on each of the right and left sides of the display area 22. Alternatively, the active matrix substrate 20 may include only one scan signal line drive circuit 32. In addition, signals which are supplied to the wiring 35 may be supplied from the driver 33.
(Patent Literature 1)
A specific arrangement of a scan signal line drive circuit is described, for example, in Patent Literature 1.
FIG. 10 is a layout diagram representing an arrangement of a major part of a scan signal line drive circuit described in Patent Literature 1.
As illustrated in FIG. 10, in a frame area of an active matrix substrate 100, there are provided a scan signal line drive circuit 400, wires 122 for a scan signal line drive circuit, and connecting lines 172. The wires 122 include clock wires.
The scan signal line drive circuit 400 includes driver TFT elements T5, T6, T10, T11, and T41 to T45, etc. The wires 122 apply signals needed by the driver TFT elements either directly or via the connecting lines 172.
Note that a wire 122 and a corresponding connecting line 172 are electrically connected to each other via two contact holes 200.